Is there a massive black hole at the center of our galaxy, the Milky

Question 3

As you suggest, if scientists were wrong about the energy radiated by the galactic center of the milky way, that could solve the "serious problem." More specifically, if the actual energy were a few thousand times higher than the energy measured by scientists, that would fix the issue.

But that's not exactly what (E) is saying. In fact, (E) is talking about the energy radiated by "a black hole." In other words, it's talking about black holes in general. Put another way, it's telling us that black holes in general actually radiate far more energy that currently thought (i.e. currently assumed).

To solve the "serious problem," on the other hand, we'd need to be told that the "galactic center" itself is radiating a thousand times more energy than scientists have determined. In other words, we'd need information about the specifics of the milky way center, not black holes in general.

In fact, if black holes in general radiated more energy than currently thought, that would make the "serious problem" even worse. On the one hand, the evidence tells us that the energy radiated is a thousand times less than it should be, if there really were a black hole. On the other, (E) tells us that the amount of energy a black hole should radiate is ACTUALLY a thousand times higher than what is currently thought. If that were the case, the discrepancy between the amount of energy the scientists measured and what it should be would be even larger.

Overall, since (E) fails to solve the "serious problem" (and actually makes it worse), we can reject it.

I hope that helps!

I have issue with the explanation of Question 2.

As you mentioned "However, if it were discovered that the matter engulfed were several thousand times less than previously estimated, the relatively low level of radiated energy observed would no longer seem at odds with the existence of the hypothesized black hole."

A. Current assumptions about how much matter a black hole would engulf proved to be several thousand times too high.
B. Current assumptions about how much matter a black hole would engulf proved to be a few thousand times too low.

So option A is opposite and option B fits in.
Hence, could you please check the option and correct me if my understanding is wrong.

I m with you, I checked on Option B too.....Please someone help us out

I am with both of you
can anyone help us out with question number 3

Matter that is engulfed at the center of the galaxy is thousands times lower than that would engulfed by a black hole (according to current assumption); Hence, if the matter engulfed by the black hole, according to the current assumption, is proved to be way higher than actual one, we can solve the problem. Option A is saying exactly the same.

And this confuses me. Because if there is a threshold to the amount of mass that can be engulfed as a black hole, then the amount of radiation(energy) coming from the center of the galaxy might be indicating something completely different and not even a black hole.

So under what assumptions are we making the decision that it is a black hole ?

Am i missing something silly here ?

GMATNinja: For #3, we have problem with less energy radiating.Option E says mote energy is radiated. What is wrong with E.

QUESTION 1: TYPE - PRIMARY PURPOSE QUESTION TYPE



You can reach the answer quite quickly from the first two sentences of the passage. (Highlighted in Blue)
Is there a massive black hole at the center of our galaxy, the Milky Way? The evidence is inconclusive.

The passage suggests that the evidence known can't conclude if there's a black hole in the center or not. If you read through the rest of the passage, we never answer that question.
Answer is D

QUESTION 2: TYPE - DETAIL QUESTION TYPE
This means that the answer should be in the passage!




Only Answer Choice C states that there's a large mass in the center of the universe.

E is a tempting answer, but there's nothing in the highlighted part (in the passage) that suggests that the mass is actually a blackhole



⠀⠀⠀⠀⠀⠀⠀⠀

Uh, I get what you are saying but I still have a different perspective.
Scenario: In the earlier para, it was mentioned that the body is most probably a black hole but it's confusing because it is not emitting as much matter as it should. 'as it should' is basically what the scientists know up till date which is a very high number.

Solution: what happens if this very high number falls? Then there is no discrepancy and they can confidently conclude that it is a black hole.
Hence, Option B seems right to me. Can anyone please help me out?

But when the energy coming from the
(25)  galactic center is compared to widely held predictions
⠀⠀⠀ based on how much matter should be falling into a
⠀⠀⠀ theoretical central black hole, there is a discrepancy
⠀⠀⠀ by a factor of a few thousand.[/box_in]

Although according to
⠀⠀⠀ current theory this makes the mass at the center
(15)  of the galaxy too dense to be anything but a black
⠀⠀⠀ hole, the relative lack of energy radiating from the
⠀⠀⠀ galactic center presents a serious problem.

jsound996 wrote:

[color=#0000ff]QUESTION 3: TYPE - OUT OF THE BOX THINKING
This means that the answer should be in the passage!

gmatt1476 wrote:

This passage is excerpted from material published
in 1997.
⠀⠀⠀⠀⠀⠀⠀⠀Is there a massive black hole at the center of our
⠀⠀⠀ galaxy, the Milky Way? The evidence is inconclusive.
(5)  Just as the Sun's mass can be determined, given
⠀⠀⠀ knowledge of other variables, by the velocity at
⠀⠀⠀ which its planets orbit, the mass at the center of the
⠀⠀⠀ Milky Way can be revealed by the velocities of stars
⠀⠀⠀ and gas orbiting the galactic center. This dynamical
(10)  evidence, based on recently confirmed assumptions
⠀⠀⠀ about the stars' velocities, argues for an extremely
⠀⠀⠀ compact object with a mass two to three million
⠀⠀⠀ times the mass of our Sun. Although according to
⠀⠀⠀ current theory this makes the mass at the center
(15)  of the galaxy too dense to be anything but a black
⠀⠀⠀ hole, the relative lack of energy radiating from the
⠀⠀⠀ galactic center presents a serious problem. A black
⠀⠀⠀ hole's gravity attracts surrounding matter, which
⠀⠀⠀ swirls around the black hole, emitting some energy
(20)  as it is engulfed. Scientists believe that the amount of
⠀⠀⠀ energy that escapes the black hole should be about
⠀⠀⠀ 10 percent of the matter's rest energy (the energy
⠀⠀⠀ equivalent of its mass according to the equation
⠀⠀⠀ E=mc^2). But when the energy coming from the
(25)  galactic center is compared to widely held predictions
⠀⠀⠀ based on how much matter should be falling into a
⠀⠀⠀ theoretical central black hole, there is a discrepancy
⠀⠀⠀ by a factor of a few thousand.

3. The “serious problem” referred to in line 17 could be solved if which of the following were true?

A. Current assumptions about how much matter a black hole would engulf proved to be several thousand times too high.
B. Current assumptions about how much matter a black hole would engulf proved to be a few thousand times too low.
C. The object at the center of the Milky Way turned out to be far more dense than it is currently estimated to be.
D. The object at the center of the Milky Way turned out to be far more massive than it is currently estimated to be.
E. Matter being engulfed by a black hole radiated far more energy than is currently assumed.

RC60500.01-30

Source : Looking Toward a Black Hole Astronomy September 1997

Serious Problem Listed in the passage:
"the relative lack of energy radiating from the galactic center" Leads to => "there is a discrepancy by a factor of a few thousand."

We are trying to resolve this problem:
So if we know that there's a relative lack of energy radiating from the galactic and the discrepancy is by a factor of a few thousand, this means that discrepancy is below the real value.
To compensate that, you need to have the assumption that there's actually more energy radiation (more matter engulfed) emitted from the galactic center than what is originally known

Only A does so, so A is correct!

3. The "serious problem" referred to in line 17 could be solved if which of the following were true?

A. Current assumptions about how much matter a black hole would engulf proved to be several thousand times too high.
B. Current assumptions about how much matter a black hole would engulf proved to be a few thousand times too low.
C. The object at the center of the Milky Way turned out to be far more dense than it is currently estimated to be.
D. The object at the center of the Milky Way turned out to be far more massive than it is currently estimated to be.
E. Matter being engulfed by a black hole radiated far more energy than is currently assumed.

Hi,
I am unable to understand why option A is correct and E is not.
"Although according to current theory this makes the mass at the center of the galaxy too dense to be anything but a blackhole, the relative lack of energy radiating from the galactic center presents a serious problem."
I don't understand how is A correct. If the amount of matter a black hole would engulf is proved to be several thousand times too high then wouldn't that mean that the black hole should radiate even more energy than it already does. This doesn't solve the serious problem which states that there is a lack of energy radiating from the center.
Whereas E states that far more energy is currently radiated so then the problem of lack of energy radiated from the center will be solved. So shouldn't this be the correct answer?

2. According to the passage, the dynamical evidence referred to in lines 9–10 supports which of the following?

A. Recent assumptions about the velocities of stars
B. Widely held predictions about the amount of matter a black hole will engulf
C. The existence of an extremely dense object at the center of the Milky Way
D. The contention that too much energy is coming from the mass at the Milky Way's galactic center for that mass to be a black hole
E. The conclusion that a compact object of two to three million times the mass of our Sun is too dense to be anything but a black hole

I understand why C is the correct answer. But the passage states that “This dynamical evidence, based on recently confirmed assumptions about the stars' velocities, argues for an extremely compact object with a mass two to three million times the mass of our Sun. Although according to current theory this makes the mass at the center of the galaxy too dense to be anything but a blackhole, the relative lack of energy radiating from the galactic center presents a serious problem”
So option E “The conclusion that a compact object of two to three million times the mass of our Sun is too dense to be anything but a black hole” Cant we say that although the lack of energy radiating from the center proves otherwise, the dynamical evidence supports the fact about compact object and hence the current theory that it cannot be anything but a black hole?

Hi GMATNinja

Please help with Question 3.

Thanks

Had the exact same thought. If this evidence didn't support this conclusion, then it wouldn't be inconclusive. We could use the energy to conclusively say there is not a black hole at the center. The energy calls the conclusion into question, but the density or dynamic evidence is the only supporting evidence given that there is a black hole at the center.

Both options A & B talks about CURRENT Assumptions, i.e. Because the scientists assumed that the amount of matter engulfed by the black hole was too high, the amount of energy expected to be radiated must also be high. But as per the last line of the paragraph, 'But when the energy coming out of the galactic center is compared to the widely held predictions ..... there was a discrepancy of a factor of a few thousand' , so the actual amount of energy radiated is less.

The question asks you to show a way in which you can solve this problem OR to resolve the flaw. The flaw is that the current assumptions about how much matter a black hole would engulf proved to be too high (it must be low, in order to solve the discrepancy).
So it must be A.

I believe option A is worded in a tricky manner but is the right answer.

Hope I helped.

Let me try question 3 for you guys:

Basically the serious problem described in the passage is that the mass discovered is assumed to be a black hole, so the black hole needs to have two properties: it should be dense and it should be emitting certain energy. The passage has explicitly stated that the mass is dense but the theory clearly mentions the lack of energy is a serious problem.

Further, the passage goes on to proceed with the explanation of the ideal energy/energy parameters as per theory, but when the actual energy emitted is compared, the difference is by few thousands. (mentioned last line)

So how does one solve this problem of energy being less in the hole/mass discovered? It is by certain assumptions which say that the energy engulfing the mass is high.
Hence A.

Hope this helps

Need help for Q3.

I think E should be the correct answer.

Have you tried reviewing this post?